Savannah Cardew, MD, FRCP(C), Osteoporosis Program, University Health Network and Mount Sinai Hospital, University of Toronto, Toronto, ON.
Successful management of osteoporosis includes nonpharmacologic and pharmacologic strategies, aimed at fracture prevention. First-line therapies include oral bisphosphonates, an intravenous bisphosphonate (zoledronic acid) that is administered once yearly, the selective estrogen receptor modulator raloxifene and parathyroid hormone. Other selective estrogen receptor modulators are being investigated as potential therapies. Strontium ranelate and denosumab each have a unique mechanism of action and may eventually be available in Canada for the management of osteoporosis. In this article the aforementioned therapies will be reviewed with an emphasis on their efficacy in preventing fractures.
Key words: osteoporosis, osteoporotic fractures, zoledronic acid, parathyroid hormone, raloxifene.
A recent study has suggested that Raloxifene may be more effective in preventing breast cancer in women with higher levels of estradiol. It has previously been shown that the risk for breast cancer increases with increased levels of endogenous estradiol. Scientists hypothesized that raloxifene, which competes with estradiol for binding to estrogen receptors in breast tissue, might have a greater effect on breast cancer risk in women with relatively high estradiol levels. They analyzed data from the Multiple Outcomes of Raloxifene Evaluation (MORE) trial, conducted in 7,290 women (80 or younger) with osteoporosis. Serum estradiol concentrations were measured by a central lab. They found that in the placebo group, women with estradiol levels greater than 10 pmol/L (2.7 pg/mL) had a 6.8-fold higher rate of breast cancer than did women with undetectable estradiol levels. Women with estradiol levels greater than 10 pmol/L in the raloxifene group had a rate of breast cancer that was 76% lower when compared to that of women in the placebo group with similar levels of estradiol. In contrast, women with undetectable levels of estradiol had similar breast cancer risk whether or not they were treated with raloxifene. If confirmed, this suggests that measuring estradiol and treating women with high estradiol levels could substantially reduce the rate of breast cancer among postmenopausal women.